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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '311ff7bd206f707abf1eedc5c65f6c94dc9bf9a1655ca5198ccc259bf13a1e42' 
  AND token = 'Y96ijdiO9UIq6UmQtwiCIbA7/9O/Z8tXQ50PY2KuPBE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}